<!DOCTYPE html
  PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<!-- saved from url=(0014)about:internet -->
<html xmlns:MSHelp="http://www.microsoft.com/MSHelp/" lang="en-us" xml:lang="en-us"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<meta name="DC.Type" content="reference">
<meta name="DC.Title" content="write_once_node Template Class">
<meta name="DC.subject" content="write_once_node Template Class">
<meta name="keywords" content="write_once_node Template Class">
<meta name="DC.Relation" scheme="URI" content="../../reference/flow_graph.htm">
<meta name="DC.Relation" scheme="URI" content="message_passing_protocol.htm">
<meta name="DC.Format" content="XHTML">
<meta name="DC.Identifier" content="write_once_node_cls">
<meta name="DC.Language" content="en-US">
<link rel="stylesheet" type="text/css" href="../../intel_css_styles.css">
<title>write_once_node Template Class</title>
</head>
<body id="write_once_node_cls">
 <!-- ==============(Start:NavScript)================= -->
 <script src="..\..\NavScript.js" language="JavaScript1.2" type="text/javascript"></script>
 <script language="JavaScript1.2" type="text/javascript">WriteNavLink(2);</script>
 <!-- ==============(End:NavScript)================= -->
<a name="write_once_node_cls"><!-- --></a>

 
  <h1 class="topictitle1">write_once_node Template Class</h1>
 
   
  <div> 
	 <div class="section"><h2 class="sectiontitle">Summary</h2> 
		 
		<p>A template class that is a 
		  <span class="keyword">graph_node</span>, 
		  <span class="keyword">receiver&lt;Input&gt;</span> and 
		  <span class="keyword">sender&lt;Output&gt;</span>. A 
		  <span class="keyword">write_once_node</span> represents a buffer of a single item
		  that cannot be over-written. The first put to the node sets the value. The
		  value may be cleared explicitly, after which a new value may be set. Gets from
		  the node are non-destructive. 
		</p>
 
		<p>Rejection of messages by successors is handled using the protocol in
		  the Message Passing Protocol, see link below. 
		</p>
 
		<p><span class="keyword">T</span> must be copy-constructible and assignable 
		</p>
 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Syntax</h2> 
		 
		<pre>template &lt; typename T &gt; class write_once_node;</pre> 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Header</h2> 
		 
		<pre>#include "tbb/flow_graph.h"</pre> 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Members</h2> 
		 
		<pre>namespace tbb {
namespace flow {
 
template&lt; typename T &gt;
class write_once_node :
  public graph_node, public receiver&lt;T&gt;,
  public sender&lt;T&gt; {
public:
    write_once_node( graph &amp;g );
    write_once_node( const write_once_node &amp;src );
 
    // receiver&lt;T&gt;
    typedef T input_type;
    typedef sender&lt;input_type&gt; predecessor_type;
    bool try_put( const input_type &amp;v );
    bool register_predecessor( predecessor_type &amp;p );
    bool remove_predecessor( predecessor_type &amp;p );
 
    // sender&lt;T&gt;
    typedef T output_type;
    typedef receiver&lt;output_type&gt; successor_type;
    bool register_successor( successor_type &amp;r );
    bool remove_successor( successor_type &amp;r );
    bool try_get( output_type &amp;v );
    bool try_reserve( output_type &amp;v );
    bool try_release( );
    bool try_consume( );
 
    bool is_valid( );
    void clear( );
};
 
}
}</pre> 
		
<div class="tablenoborder"><table cellpadding="4" summary="" frame="border" border="1" cellspacing="0" rules="all"><span class="tabledesc">The following table provides additional information on the
			 members of this template class. 
		  </span><thead align="left"> 
				<tr> 
				  <th class="cellrowborder" valign="top" width="33.89830508474576%" id="d87805e152">Member 
				  </th>
 
				  <th class="cellrowborder" valign="top" width="66.10169491525423%" id="d87805e155">Description 
				  </th>
 
				</tr>
</thead>
 
			 <tbody> 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">write_once_node( graph &amp;g
						)</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Constructs an object of type 
						<span class="keyword">write_once_node</span> that belongs to the 
						<span class="keyword">graph g</span>, with an invalid internal buffer
						item. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">write_once_node( const
						write_once_node &amp;src )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Constructs an object of type 
						<span class="keyword">write_once_node</span> with an invalid internal
						buffer item. The buffered value and list of successors is NOT copied from 
						<span class="keyword">src</span>. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool try_put( const input_type
						&amp;v )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Stores<span class="keyword"> v</span> in the internal single item
						buffer if it does not already contain a valid value. If a new value is set, it
						calls 
						<span class="keyword">try_put(v)</span> on all successors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool register_predecessor(
						predecessor_type &amp;p )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Never rejects puts and therefore does not need to maintain a
						list of predecessors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool remove_predecessor(
						predecessor_type &amp;p )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Never rejects puts and therefore does not need to maintain a
						list of predecessors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool register_successor(
						successor_type &amp;r )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Adds 
						<span class="keyword">r</span> to the set of successors. If a valid
						item 
						<span class="keyword">v</span> is held in the buffer, a task is
						spawned to call 
						<span class="keyword">r.try_put(v)</span>. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool remove_successor(
						successor_type &amp;r )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Removes 
						<span class="keyword">r</span> from the set of successors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool try_get( output_type &amp;v
						)</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>If the internal buffer is valid, assigns the value to 
						<span class="keyword">v</span>. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if 
						<span class="keyword">v</span> is assigned to. 
						<span class="keyword">false</span> if 
						<span class="keyword">v</span> is not assigned to. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool try_reserve( output_type
						&amp;v )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Does not support reservations. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool try_release( )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Does not support reservations. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool try_consume( )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Does not support reservations. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">bool is_valid( )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if the buffer holds a valid value,
						otherwise returns 
						<span class="keyword">false</span>. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d87805e152 "><span class="keyword">void clear( )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d87805e155 "> 
					 <p>Invalidates the value held in the buffer. 
					 </p>
 
				  </td>
 
				</tr>
 
			 </tbody>
 
		  </table>
</div>
 
	 </div>
 
  </div>
 
  
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong>&nbsp;<a href="../../reference/flow_graph.htm">Flow Graph</a></div>
</div>
<div class="See Also">
<h2>See Also</h2>
<div class="linklist">
<div><a href="message_passing_protocol.htm">Message Passing Protocol 
		  </a></div></div>
</div>

</body>
</html>
